Magnetically controlled timing assembly



Nov. 8, 1966 R. w. LENHARDT 3,

MAGNETICALLY CONTROLLED TIMING ASSEMBLY Filed June 22, 1964 5 Sheets-Sheet 1 IN VENTOR.

ROBERT W LENHARDT B A T TORNEY.

Nov. 8, 1966 R. w. LENHARDT 3,284,746

MAGNETICALLY CONTROLLED TIMING ASSEMBLY Filed June 22, 1964 5 Sheets-Sheet 2 5| h @3 Q I 29 $45 M II' WNW- Hii- 1;; l INVENTOR. 3596 ROBERT W. LENHARDT.

A TTORNEY Nov. 8, 1966 R. w. LENHARDT 3,284,746

MAGNETICALLY CONTROLLED TIMING ASSEMBLY Filed June 22, 1964 5 Sheets-Sheet 3 FIELD IN TENS/TX DEGREES OF MACHINE CYCLE.

9s Fig.5.

INVENTOR.

ROBERT M. LENHARDI BY ATTORNEY.

United States Patent ()fiice 3,284,746 Patented Nov. 8, 1966 3,284,746 MAGNETICALLY CONTROLLED TIMING ASSEMBLY Robert W. Lenhardt, Milford, Mich., assignor to Burroughs Corporation, Detroit, Mich., a corporation of Michigan Filed June 22, 1964, Ser. No. 376,625 7 Claims. (Cl. 335237) This invention relates to a magnetically controlled timing assembly and, in particular, to an assembly of magnetically actu-atable switches, the accurately timed operation of each of which is controlled by an interposed rotating member having several portions of different flux shunting capacity.

The high speed cyclical operation of a mechanism, such as an electro-mechanical computer, requires the maintenance of an especially accurate timing relationship between several of its portions. In the past, timing devices utilizing mechanical switches have been employed. After a period of high speed us'eage, these timing devices become inaccurate due to the inability of their elements to maintain especially close tolerances. A high incidence of switch failure also arises due to wear and fatigue of the elements. Accordingly, such timing devices require considerable adjustment and frequent parts replacement.

More recently, the use of magnetically controlled reed contact switches has greatly improved the switching characteristics of timing devices. The reed switch element referred to herein is well known in the art and comprises a small switch having a pair of resilient contact leaves encapsulated in a reducing or an inert atmosphere. The contact leaves are of a magnetizable material and act as armatures when under the influence of a magnetic field supplied by an external source. Means are employed to shunt and distort the flux coupling the source to the switch and thereby effect switching action.

The means commonly employed to alter the quantum of flux coupled to the switch is a magnetizable element having only one flux shunting capacity. Relative motion between the switch and the shunting element varies the distance therebetween which results in variations in the coupled magnetic energy. When graphically represented as a field intensity curve, the coupled flux has a continuously changing slope "between its maximum and minimum level. The switch is designed to make and break between these two levels.

As inherent to many switching elements, the reed switch requires a greater quantum of energy to close or make it than to hold it closed; hence, the make and break levels I are vertically displaced on a field intensity curve. Since the slope of the curve is continuously changing and the accurate operation of the switch depends upon locating two switching points each lying at a diflerent energy level and separated by time on the intensity curve, a noteworthy problem exists if a high degree of accuracy is required. This problem is compounded by the use of a plurality of switches, each controlling one portion of the computer or other utilization mechanism, the operation of which has a timed interrelationship with other portions of the mechanism, and is further magnified because of manufacturing tolerances which can cause the switching levels of each switch in the assembly to vary by at least a few percent from those of the other switches.

The present invention provides a plurality of switching I units each primarily comprising a reed switch, a permanent magnet, and an interposed cyclically operated flux shunting element having portions of different flux shunting capacity which enables the switch to be coupled with several levels of field intensity and thereby increases the accurate determination of the make and break points.

More particularly, the flux shunting elements of the timing assembly are a plurality of axially aligned disks of non-magnetic material having aflixed to each of their obverse and reverse faces a radial segment of high permeability foil having a leading and a trailing edge. The leading edges of the two foils on a disk are radially aligned and are positioned to be interposed exactly between the magnet and the reed switch at the switch break time. This causes the flux coupled to the switch to be diminished from a maximum level toward a minimum level with the maximum rate of change being at the break time. The trailing edge of the foil on the reverse face follows shortly after the minimum flux level is attained and reduces the flux shunting capacity of the then interposed portion of the timing disk to thereby increase the field coupled to the switch to an intermediate level between the minimum and making levels. The trailing edge of the foil on the obverse face of the timing disk is then positioned so that it is interposed at the exact moment of the making of the switch contacts, which is at a higher level than the breaking point and is also during the maximum rate of change of field intensity between the intermediate and maximum field levels. After the trailing edge of this foil passes the switch, maximum flux coupling is again achieved. Variations in the radial extent and position of the foils on the several disks determine the timing relationships between the opening and closing of their associated switches which thereby regulate the timed interrelationship of the computer portions they control.

Accordingly, it is one object of this invention to provide a timing assembly having improved accuracy and durability.

Another object of this invention is to provide a magnetically controlled timing assembly in which the timing of the make and break of the switches is accurately predetermined.

Another object of this invention is to provide a magnetically controlled timing assembly having switching characteristics which are regulated by control means having multiple flux shunting capacities.

Another object of this invention is to provide a cyclically operated timing assembly having magnetic switches each of which are subject to three distinct levels of field intensity.

Another object of this invention is to provide a magnetically switched timing assembly in which switching action arises during periods of maximum rate of change of a variable field intensity.

A further object of this invention is to provide a timing assembly having a compact arrangement of magnetic switching units which are efiiciently shielded from each other.

Other objects and features of this invention will become apparent from the following description when read in conjunction with the accompanying drawings wherein:

FIG. 1 is a perspective view of the invention and a portion of the framework of the system in which it is housed;

FIG. 2 is a top view of a portion of the subject timing assembly, showing several of the switching units;

FIG. 3 is an end view of the portion of the assembly shown .in FIG. 2;

FIG. 4 is a graph of time versus field intensity during the cyclical operation of two of the switching units; and

FIGS. 5 and 6 are side views of two of the timing disks particularly showing the positioned foil segments.

The subject magnetically controlled timing assembly is capable of regulating the timing operations of a wide range of systems and devices. The following described embodiment is particularly suited to offer close tolerance timing necessary for the successful operations of an electro-mechanical computer. Y

.. and sealed in a glass envelope 61.

by approximately 90.

Referring first to FIG. 1, in which the timing assembly is designated 11, there are shown fragments of the main sideframes 13 of a computer, between which sideframes is secured a tie bar 15. Attached to the foremost main sideframe and spaced therefrom is an auxiliary sideframe 17. A drive shaft 19 passes through the adjacent sidefrarnes 13 and 17 and is rotatably journaled therein by a pair of bearings 21. To the end of the drive shaft, proximate the auxiliary sideframe 17, is affixed a sprocket 22 which is coupled by mechanism, not shown, to the main driving means of the computer, also not shown, such that there is a direct cyclical relationship between the drive means and side of the wafer.

the braces in spaced parallel relation. Each support rod, 1

is provided with spaced radial grooves, not shown, and into each of said grooves is seated a retaining clip 31. Journaled between the braces 23, in a pair of bearings 33, is a timing shaft 35 which is joined to the drive shaft 4 side 43 of the wafer, with the opposite facet 71 lying flush with the front side 45 of the wafer, as shown 'in FIG. 2. A non-rnagnetic spacer 73 is afiixed to the front side of the mounting wafer to cover the facet of the magnet that is exposed through the wafer slot 67 and thereby provides the same amount of non-magnetic environment that the mounting wafer would have provided if the magnet were secured to the surface of the rear A high permeability flux shunting shield 75 is fixed to the exposed surface of the spacer 73.

Thus, a reed switch 57 and a permanent magnet 65 mounted to opposite sides of each wafer 39, are separated by a relatively large distance, and are provided with flux shunting shields '63 and 75. Further, as shown in FIGQZ, the above described elements are mounted on adjacent wafers in an alternate manner so that the facet 69' of the magnet, exposed on the rear side of one wafer, such as 39C, faces toward the reed switch on the front side of the next wafer, such as 39D, with the magnetic poles respectively aligned with the fixed ends of the armatures. Assembled in this manner, the reed switch on any particular 19 by a coupler 37 which is positioned between the fore 1 most main sideframe 13 and the adjacent brace 23. The drive and timing shafts 19 and 35, joined by the coupler 37, are employed to eliminate the problem of accurately aligning a single shaft through the timing assembly and nism.

Component mounting wafers 39A-H, of electrically non-conductive and non-magnetic material, are positioned along the support rods 29 in spaced parallel relation. As

. shown in FIGS. 1 and 3, the wafers are generally trapezodial in profile and have front and rear sides 41 and 43 having circular apertures 45 near each corner, through which pass the support rods 29. The wafers are firmly held in position by the retaining clips 31 which lie on one side of each Wafer and by small springs 47 which are coiled around the support rods and lie between alternate wafers forcing them against their respective retaining clips.

As shown in FIG. 3, there are formed on the front side 41 of each mounting wafer printed circuit conductors 49 .which connect a first pair of pads 51 to a second set of rate portions of the electronic logic section of the computer. Mounted across the pads 51 is a read switch 57, of the type described above, having a pair of magnetizable leaves or armatures 59 which are normally spaced apart The switch 57 lies radial to the timing shaft 35 and is displaced about 45 from vertical with reference to the base of the wafer. A high permeability flux shunting shield 63 is affixed to the rear side 43 of each mounting wafer 39 directly behind and covering a larger surface area than the reed switch 57.

A small permanent bar magnet 65 of high magnetic strength or intensity and having a size similar to that of the reed switch is also positioned on the rear side of the mounting wafer. The magnet is also oriented radial to the timing shaft and is displaced from the reed switch To establish a more uniformly predictable magnetic field pattern, all of the magnets should have a common pole directed toward the timing shaft and the switch should be oriented such that the'air gap between its leaves lies perpendicular to the plane of the mounting wafer. Although the magnet could be affixed to the surface of the rear side of the mounting wafer, the packing density of the entire timing assembly is increased by seating the magnet in a slot 67 in the wafer. The imbedded magnetis positioned so that one of its facets 69 extends slightly outward from the rear then through the sideframe members to the drive meohamounting wafer is magnetically coupled to the magnet it faces on a next adjacent wafer and is magnetically isolated from all other magnets in the timing assembly.

Timing disks 77A-G are respectively interposed between the mounting wafers 39A-H and are supported by hubs 79 which are axially spaced along the timing shaft and are adjustably secured thereto by set screws 81 which thread through the hubs and seat against the timing shaft. The timing disks are of a non-magnetic material, i.e., a

material having a permeability approaching unity. Each disk 77 has an obverse face 83 which is juxtapose to the front side 41 of one adjacent mounting wafer 39 and its reed switch 57, and each disk has a reverse face 85 which lies opposite the rear side 43 of the other adjacent mounting wafer and the outward extending facet 69 of its magnet 65.

Aflixed respectively to the obverse and reverse face of each timing disk is a major or overlay switching foil 87 and a minor or backup switching foil 89, each of a material exhibiting high magnetic permeability and correspondingly high flux shunting capacity. Each switching foil has an annular portion 91 adjacent the disk hub 79 and radial portion 93 extending therefrom, as shown in FIGS. 1, 5, and 6. The radial portion of each foil has a leading edge 95 and a trailing edge 97. The angular displacement between the leading and trailing edges of the major foil 87, which faces the reed switch on the adjacent mounting wafer 38, is somewhat greater than the angular displacement between edges of the minor foil 89, which faces the exposed facet 69 of the magnet on its adjacent mounting wafer 39, is somewhat greater than the angular portions on both faces of a timing disk are radially coincident or aligned and their trailing edges 97 are dis placed. This manner of construction provides a considerable flux shun-ting capacity adjacent the aligned leading edges, less shunting capacity adjacent and subsequent to the trailing edge of the backup foil, and virtually no shunting capacity radially subsequent to the trailing edge of the overlay foil, thus, enabling the development of the aforementioned multi-leveled field intensity which is coupled to the switch during rotation of the timing disk.

As shown, in FIG. 5, the leading edge of the foils on the disk 77C commence at 85, the trailing edge 97 of the backup foil 89 lies at and the trailing edge 97 of the major foil 87 lies at 300. This particular positioning of the radial foil portions will, as subsequently described in detail, cause the reed switch on the wafer 39D to open at or near 85 and close at or near 300 of the machine 7 cycle. The accuracy of the closing of the switch will be foil 89.

The angular position of the foil edges is measured from a zero degree reference point 99 on each timing disk. During the fabrication of the timing assembly, the timing shaft 35 is held stationary and the zero reference point on each of the disks is aligned with its associated reed switch such that it bisects the geometric projection of the air gap between the armatures 59. Accordingly, there is a 90 shift between the zero reference position on the faces of the disk 77C in FIG. 5 and the position on the similar faces of the disk 77D in FIG. 6, since the corresponding reed switches on the mounting wafers 39D and 39E are displaced by 90. After the alignment of the timing shaft and timing disks with respect to the switches, the timing shaft 35 is coupled through the drive shaft 19 to the main cyclical driving means of the computer such that the driving means, which also has a zero degree reference point,- and the timing disks are synchronized with their Zero points coincident. In this manner, the operation of the computer through one machine cycle of 360 drives the timing disks through a corresponding 360.

In order to increase the amount of magnetic flux coupling a particular magnet on one mounting wafer to its associated reed switch on an adjacent wafer, reduce the effects of stray flux, and also increase the packing density, each wafer 39 is formed with a semicircular cutout 101 which, as shown in FIGS. 1 and 3, is aligned with and has a diameter slightly larger than the disk hub 79. The cutout 101 allows clearance for the hub 79 and enables the obverse face 83 of the disk and its switching foil 87 to be positioned as close as desired to the front side 41 of the mounting wafer and its reed switch 57.

As earlier described the magnet 65 is imbedded in the wafer and only extends outward a short distance from the rear side 43 of the wafer; therefore, the reverse face 85 of the disk and its switching foil 89 can be made to lie very close to the rear side of the wafer.

The timing assembly constructed as above set forth provides a plurality of closely positioned, magnetically isolated, switching units each primarily comprising a permanent magnet anda reed switch mounted on adjacent wafers in facing relation and an interposed foil-faced timing disk coupling the magnet to the switch with a plurality of levels of magnetic field intensity to effect an especially accurate relationship between the cyclical rota- I tion of the timing disk and the switch actuation. The unique operation of each switching unit is predicated upon Y the interposition of a structure which has portions each exhibiting different flux shunting capacities. This salient feature of the subject timing assembly will be elaborated upon below with reference to its operation and the graphs in FIG. 4.

Before presenting a detailed discussion of the operation of the subject invention, some of the magnetic and mechanical specifications of the elements of a preferred embodiment will be set forth. It of course is to be appreciated that the teachings of this invention are not limited to such specifications and that they are herein provided to assist one skilled in the art to apply the inventive teachings to timing assemblies with which he may be concerned, which, because of their environment, may require variations in the parameters.

Mounting wafer 39 Material: Glass-epoxy Height: 1.75"

Bases: 4" and 2.25"

Thickness: 0.062"

Reed switch 57 Length: 0.75"

Diameter: 0.125"

Make level: 40 ampere-turns Break level: 30 ampere-turns Tolerances: A maximum of i7 /2 ampere-turns for each level and a minimum of 4 /2 ampere-turns between levels.

6 Magnet 65 Material: Alnico V (51% Fe, 24% Co, 14% Ni, 8%

Al, 3% Cu) Typical retentivity: 12.5 kilogauss Cross section: 0.093 Length: 0.75"

Timing disks 77 Material: Non-magnetic stainless steel (70% Fe, 18% Cr,

9% Ni, 1% Si) Diameter: 3"

Thickness: 0.020"

Switching foils 87, 89Shunting shields 63, 75

Material: High permeability, low retentivity Mu Metal (77% Ni, 15% Fe, 5% Cu,'1.5% Cr) Thickness: 0.006"

Spacer 73 Material: Phenolic Thickness: 0.031"

It has been found very satisfactory to bond the foils to the disks and the shunting shields and spacers to the wafers with adhesives of low permeability. If the mounting wafers are spaced apart about 0.20" by the retaining clips 31 and the springs 41, and the timing disks are positioned so that an equal distance of about 0.015" lies between the switching foil 87 and the switch envelope 61 and between the switching foil 89 and the facet 69 of the magnet, optimal switching conditions should prevail.

With respect to the operation of the -timing assembly, basic magnetic theory teaches that the lines of flux linking a source, such as the bar magnet 65, to a magnetizable medium lying longitudinally adjacent thereto, such as the switch armatures 59, emanate from the source in a flux density pattern that is greatest at the poles and least therebetween. Also, the flux pattern between a pole and a magnetizable medium has a maximum density along the shortest path therebetween. Accordingly, when an interposer of high magnetic permeability is translated at a uniform rate of speed from a location distance from the switch and magnet, to a location between two such closely positioned elements with the leading edge of the interposer well past the perpendicular bisector therebetween, the magnetic flux coupled to the switch decreases from maximum to minimum in such a manner that a field intensity curve plotted therefrom would appear as shown in FIG. 4 by the dotted curve 103 between 0 and 180.

FIG. '4 is a graph of unity field intensity, subdivided by tenths, versus rotation of the timing disks, subdivided by degrees of the machine cycle. As shown thereon, the first 180 of curve 103 is symmetric about its vertical midpoint 105, which is both an inflection point and also the point of greatest slope of the curve. Therefore, the portion of the curve closest to its midpoint 105 contains the greatest change of field intensity per change of time and thereby provides the most accurate switching point. For example, if the reed switch were manufactured to have a break level of .60- -.10 on the unity based field intensity curve 103, and if it were desired to open the switch at 50 of the machine cycle, an accuracy of i1 could be obtained; since at .70 the curve lies at 49 and at .50 it lies at 51, which as shown on the graph is essentially a vertical line.

However, if the switching point were closer to one of the knees of the curve, considerably more error would be introduced. The latter of the curve 103 illustrates this condition. As shown, this portion of the curve 103 is the mirror image of the first 180, having its vertical midpoint 105 at the same .60 field intensity level as the corresponding midpoint 105. This segment of the curve would be formed during the removal of the flux shunting interposer, the terminatioin of its interposition occurring, for example, at 320. As previously pointed out, the make and break levels of a reed switch are significantly displaced; therefore, let it be assumed that the switch closes at .75:.10 field intensity, which when related to the .60-1210 break level represents a very high quality close tolerance switch. Although a high quality reed switch is employed, the latter half of curve 103 crosses, the lower tolerance level of .65 at 320, the make level of .75 field intensity at 323 and the upper tolerance lever of .85 at 329. Thus, the switch making point of .75 occurs 3 later than the desired time of 320 and the total range about this point is 9, which would allow for more than four times as much error as the il range about the breaking point.

It will be appreciated that even a few degrees of error creates a serious problem. If the timing shaft 35 were rotating at approximately 165 rpm. one degree of a 'machine cycle would equal one millisecond; therefore,

three or four degrees of error would represent too much timing inaccuracy with reference to the control of the logic elements of a computer for the computer to function reliably. Accordingly, suitable timing accuracy cannot be provided for an utilization device, such as an electro-mechanical computer, which employs a simple, high 1 permeability interposer which periodically cuts the flux pattern and whose operation is represented by the field intensity curve 103 of FIG. 4.

It is necessary, as taught herein, to employ a more complex magnetic field controlling means having portions of different flux shunting capacity which produce a bisegmented curve 109, 109 having three distinct levels of field intensity, in this manner, one of the curve segments 109 has its midpoint 111 at the switch breaking level and the other curve segment 109' is shifted vertically upward, has a smaller vertical excursion, and has its midpoint 111' at the switch making level.

The operation of the subject timing assembly will be explained with particular reference to two of the magnetically isolated switching units formed by the timing disks 77C and 77D and the elements mounted on the associated wafers 39C, 39D and 39B. The orientation of the switching foils 87 and 89 on the disk 77C was earlier set forth with reference to FIG. such that the switch would open at 85 and close at 300. The resulting variable field intensity effecting the actuation of the reed switch 57 on the wafer 39D is displayed graphically on FIG. 4 by the bisegmented curve 109, 109'. The disk 77D, as shownin FIG. 6, has the leading edge 95 of its radial foil portions 93 positioned at 150 of the machine cycle, the trailing edge 97 of the backup foil 89 lies at 190, and the trailing edge 97 of the major foil 87 is radially aligned with the magnet 65 on the mounting wafer 39E at 225 of the machine cycle. The resulting variations in the field intensity are shown by the curve 113, 113 on which the respective midpoints are 115, and 115 and coincide with the switch break and make times 150 and 225 Let it be assumed that the above illustrated switching levels and tolerances are employed, i.e., .60 and .75 field intensity :L.10.

FIGS. l-3, 5 and 6 represent the positions taken by timing disks at the beginning of a machine cycle, at which time the zero degree reference point 99 on each disk is aligned with the associated reed switch. In that position, with respect to the switching unit formed by the timing disk 77C, its foils and the elements on the mounting wafers 39C and 39D, it will be observed that the parts of the surfaces of theobverse and reverse faces 83 and 85 of the disk 77C which lie immediately between the magnet on the wafer 39C and the reed switch on the wafer 39D do not carry radial foil portions 93.

. Since the non-magnetic timing disk and the adjacent air 1 form the only interposing material, the magnetic flux emanating {from the rearward facing facet 69 of the '8 'insure that the switch is closed at 0 of the machine c cle.

As the timing shaft 35 is driven clockwise during the machine cycle, the radially coincident leading edges 95 of the switching foils 87 and 89 will approach the magnet and switch and commence cutting and distorting the flux therebetween. The'double shunting thickness of the high permeability foils will cause a rapid drop in the field intensity such that the time that the level is between .70 and .60 is very close to 85 This somewhat linear excursion through the switch breaking level coincides With the passage of the leading edges of the foils 87 and 89 between the reed switch and its related magnet.

As the timing shaft 35 continues its rotation, the switching foils will continue to distort and cut additional lines of flux, thus further reducing the field applied to the .switch. However, since these additional flux lines lie in .an increasingly less dense pattern, the rate of change the switching points can be determined can be appreciably enhanced 'by having the switch opening and closing levels each lying at the midpoint of the field intensity curve. Since these levels are significantly displaced, two distinct ,midpoints 111 and 111' are necessary. Obviously, a

curve having only one maximum level and only one minimum level cannot have two vertically displaced midpoints. Hence, two curves or curve segments 109, 109' having different vertical excursions must be formed by the operation of the flux shunting interposer. Since a cyclically operated interposer is preferred, the. segments of the curve are contiguous and must have one common 1 level. If the maximum level is chosen as common and the minimum level of the first curve segment 109, whose midpoint 111 lies at the break level, is unaltered, then the minimum level of the second curve segment 109' must be shifted upward such that its midpoint 111' is coincident with the make level.

To eifect an upward shift in the minimum field intensity level of the curve segment 109', the trailing edge 97 of the backup foil 89 is positioned after the aligned leading edges 95 and in advance of the trailing edge 97 of the major foil 87. Subsequent to the passage of the trailing edge of the backup foil from the interposed position, only a single thickness of the high permeability shunting material, as provided by the major foil 87, is interposed between the reed switch and the magnet. This allows the amount of coupled flux to increase and results in the upward shifting of the field intensity curve segment 109 from its lowest or minimum level to an intermediate level, which is in fact the minimum or lowest level of the curve segment 109'. As shown, the curve begins its upward swing before the radial foil portion 93 of the backup foil terminates its interposition. This results from the fact that the flux pattern is spread over a surface area of the timing disk equal to several degrees of the machine cycle and that some of the flux crossing this area no longer is being fully distorted nor shunted because of the approach of the trailing edge 97 of the backup foil.

As earlier noted, the minimum level that the curve segment 109 attains is above the minimum level of the curve 103 but that its point of inflection 111 is at the same level as the midpoint 105. It will be appreciated that if the field intensity represented by curve segment 109 were permitted to reach a lower level before being shifted upward to the minimum level of segment 109', more time would have to elapse between the switch breaking point 111 and the attainment of the minimum level of curve segment 109'. Since the latter is a prerequisite to the accurate closing of the switch, its delay will necessitate a longer elapse of time between the breaking and subsequent making of the switch than if the curve 109 were initially prevented from going as low as the curve 103. The radial extent of the backup foil 87 can be used to regulate the amount of flux shunted away from the switch; the smaller the foil, the less shunting. The limiting factor to the minimum size of this radial foil is that it, in combination with the overlay foil 87, must adequately regulate the shunting of the field intensity so that the field is caused to fall safely below the switch break level, including the manufacturing tolerance. With reference to the afore-listed typical specifications, a backup foil covering 40 of the reverse face 85 of a disk in combination with an overlay foil on the obverse face 83 is more than sufficient. Thus, at 125 of the machine cycle, 40 past the aligned leading edges of the foils which were coincident with the 85 switch opening point, the trailing edge of the backup foil will be radially aligned between its associated reed switch and magnet.

The curve segment 109' will remain at its lowest field level as long as the major foil cuts and distorts a constant quantum of flux. The termination of the interposition of the radial portion major foil depends upon the point in the machine cycle that the switch is again to be closed. If as shown in FIG. 4, the make or close point is to be 300", then the trailing edge 97 of the major foil 87 will be positioned at 300 so that as the timing disk continues its rotation and approaches the 300 position, the total amount of flux lines being cut and distorted by the major foil will diminish at an increasing rate with the point of maximum rate of change, i.e., the inflection point 111 of the intensity curve 109', lying very close to make level .75. During the remaining 60 of the machine cycle the radial portion 93 of the major switching foil will be rotated further away from the switch until its shunting effect is at a minimum, and, correspondingly, the coupled field is again at maximum, or unity as shown.

During the next machine cycle the above described operation will be repeated: The switch on the wafer 39D will open at 85, when the aligned leading edges of the radial foils on the disk 77C are interposed; the coupled field intensity will reach first and second lower levels, the latter brought about by the termination of the radial portion of the backup foil and therefore lying at a level above the former; the switch will close at 300, when the trailing edge of the major foil passes that position; and finally the coupled flux will reach highest intensity when interposed only by the non-magnetic disk 77C.

The operation of the reed switch on the wafer 77E is controlled by the interposition by the switching foils on timing disk 77D of the flux emanating from the magnet on the wafer 39D. It will be appreciated that the physical, mechanical and magnetic relationship of these elements is the same as the relationship of the elements comprising the above described switching unit with the exception of the positions of the leading and trailing edges of the foils; hence, the operation will be the same except for the timing.

As shown in FIG. 4, the curve segments 113 and 113" follow paths respectively parallel to the curve segments 109 and 109, with the exception of the value of the minimum level of the segment 113 and the duration of the minimum level of the segment 113. The parallelism of these curves is to be expected, since switching foils which determine the curve forms provide the same several capacities of flux shunting and differ only by their duration relative to the machine cycle. If it is desired that the switch on wafer 77E be open for only 75 of the machine cycle, compared to 215 for the reed switch on wafer 77]), the trailing edge of the major foil on the disk 77D, which controls the closing of the switch on wafer 77E, is positioned closer to its leading edge and the edges of its asso- 10 ciated backup foil than was the trailing edge of the major foil on the disk 77C. Accordingly, the time duration that the curve segment 113 is at its minimum level is significantly foreshortened and the minimum level of the seg v ment 113 is slightly higher.

In a similar manner, if a switch were to be closed for a relatively short duration, the aligned leading edge of the switching foils would be displaced from the trailing edge of the major foil by a short radial extent, thus preventing the field intensity from attaining its maximum or unity level. As long as three discrete field intensity levels are obtained and each is outside of the manufacturing tolerances of its associated switching level, such that the midpoint of each curve segment lies at the designated switching level, as above described, increased timing accuracy can be obtained.

A further examination of FIG. 4 shows that the midpoints 111, 115, 111, and 115' and the curve portions adjacent thereto all lie within the most vertical sections of their respective curve segments; therefore, switching proximate these points will have a minimum of error. Since the curve segments 109' and 113 have a shorter vertical range than the curve segments 109 and 113, switching about the midpoints 111' and 115' will be slightly less accurate than switching about the midpoints 111 and 115; however, switching about these midpoints will be considerably more accurate than about the point 107 of curve 103 which, as previously described, had to lie at a substantial distance from the midpoint 105' of that curve along a curve portion having less slope.

To further insure the required timing accuracy, each reed switch and its associated magnet must be magnetically isolated from their surroundings to the extent that the formation of the three levels of field intensity and the response curves having their respective midpoints at the switching levels is fully dependent upon and controllable by the timed interposition of the foil-faced timing disks. Thus, as earlier described, the switch and magnet on each mounting wafer are aflixed on opposite sides thereof, are substantially displaced, and are provided shunting shields. The high permeability shunting shield 63, which is positioned behind each switch on the rear side of the wafer,

' has the dual purpose of isolating the switch from the effects of the magnet lying on the rearward adjacent wafer and also of isolating the switch from the variable shunting effects of the rearward positioned foil-faced timing disk. The shunting shield 75, which is located proximate to the forward facet 71 of the magnet and thus faces the shield 63, further isolates the flux emanating from that facet from being erroneously coupled to the non-associated switch on the next forward wafer. The non magnetic spacer 73 employed to separate the shield 75 from the facet 71 also has a dual purpose. It increases the shun-ting efficiency of the shield relative to flux emanating from the facet 71 and minimizes the shunting of the flux directed from the facet 69 of the magnet toward its associated switch.

The annular foil portions 91 further aid in the regulation of the flux coupling between a particular switch and its associated magnet by forming continuous high permeability flux paths away from the radial portions 93 to the hubs 79 and timing shaft 35 which are of moderate permeability. The annular portions also pass close enough to the shunting shields to increase their efiiciency and additionally will tend to shunt stray flux away from the switches.

Hereinabove one set of switching foils was described as being affixed to both sides each non-magnetic timing disk to affect one opening and closing of an associated switch during each machine cycle. Obviously more than one set of switching foils could be employed on each disk to provide more than one set of switching actions per machine cycle. Also, the foils could both be afiixed to one side of the disk without significantly altering the magnetic characteristics of the timing apparatus. It will skilled in the art that variations may be made therein 1 also be appreciated that the non-magnetic disk is employed for mechanical stability; therefore, its size and shape could be modified, or in fact it could be obviated where such stability were not a manufacturing and operational criterion. 5

This invention broadly teaches the use of a magnetic shielding which has portions providing at least three different flux shunting capacities for increasing the predetermined accuracy of a magnetic switching unit. Ac- I cordingly, any structural element or combination thereof shunting flux in this manner for this purpose is herein envisioned.

From the foregoing it will be apparent that there has been presented a practical application of the use of a plurality of closely assembled magnetically controlled switches in an especially accurate timing assembly which accomplishes all of the initially stated objects. While there have been shown and described the fundamental novel features of this magnetically controlled timing assembly in a preferred embodiment with reference to a v particular environment, it will be apparent to those the trailing edge of said other magnetic area comprises the trailing edge of one of said foils, and

the trailing edge of said other foil lies radially intermediate the edges of said one foil.

3. A switching device according to claim 2 wherein:

the means providing said magnetic field has a planar elongated body aligned with said armatures and lies in spaced parallel relation thereto,

said disk has an axis of rotation perpendicular to said armatures, and

a portion of said disk is continuously interposed between said armatures and said magnetic field means.

4. A switching unit comprising:

a rotatable disk of low magnetic permeability,

an elongated bi-poled permanent magnet fixedly positioned in spaced parallel relation to one side of said disk and radial of the axis of rotation of said disk,

a switch element fixedly positioned in spaced relation to the other side of said disk and having a pair of normally separated elongated magnetizable armatures lying perpendicular to and radial of the axis of rotation of said disk,

said armatures longitudinally aligned with said magnet and embraced by the magnetic field emanating therefrom, which when coupled to said armatures in sufiicient intensity magnetizes them of opposite polarity and causes their mutual attraction to close said switch element,

first and second magnetic members of high permeability affixed respectively to and covering portions of said without departing from the spirit of the invention.

What is claimed is:

1. In combination with a magnetically operable switch and an adjacently fixed magnet, said switch having armature means held in one position by magnetic energy from said magnet and operable to another position by shunting magnetic energy from said switch armature means, magnetic energy shunting means comprising:

a cyclically driven non-magnetic disk interposed be tween said switch and said magnet, and

a plurality of discrete arcuate segment magnetic elements carried by said disk on at least one of its sides of said rotatable disk,

said magnetic members each having a leading and a trailing edge radial of said axis of rotation,

said leading edges being radially coincident and the Surfaces, trailing edge of one of said members lying radially said magnetic elements proximately positioned with reintermediate the edges of the other member to effect spect to one another and in combination effecting a upon rotation of said disk the coupling to said armafirst quantum of magnetic energy shunting when tures of three distinct levels of magnetic intensity carried by said disk into an interposing position becausing said switch to close when the trailing edge of tween said switch and said magnet, said other magnetic member is radially coincident one of said magnetic elements extending beyond and with said armatures and said switch to open when being of greater arcuate extent and expanse than the said leading edges are radially coincident with said other element and effecting a second and lesser armatures. quantum of magnetic energy shunting when in inter- 5. A magnetically controlled switching unit comprisposing position. 2. Aswitching device comprising: a permanent magnet and a closely positioned switch means providing a constant magnetic field, element, pair of magnetizable armatures normally occupying said switch element having a pair of magnetizable armaan open position and oriented within said magnetic tures each having a stationary end lying adjacent a field to be closed by said field, respective different one of the poles of said magnet magnetic means for distorting said magnetic field wherea d a f d l i i t di th P0165 f id by the field applied t0 said armatures is insufficient magnet such that when said armatures were ener. to magnetize and cause them to assume the closed gized with a sufficient quantum of magnetic flux position, their free ends will become mutually attracted to said magnetic means having two adjacent areas exhibitlo id it h d h energized i h a lesser ing different magnetic field distorting capabilities, quantum of flux said free ends will attain a normally one of said areas having a distinctly defined leading separated orientation opening said switch, edge and the other of said areas having a distinctly a transportable interposer of substantially unity permedefined trailing edge, ability positionable between said switch and said each of said edges, when most proximate to said arma- 0 magnet parallel to said armatures,

tures, lying parallel thereto and equidistant there said interposer having an obverse face proximate said from, and switch and a reverse face proximate said magnet, means periodically moving said magnetic means to and first and second foils of similar flux shunting capacity from the vicinity of said armatures causing them to affixed to and respectively covering only a portion of periodically occupy the open position from the time 5 said obverse and reverse faces of said interposer, when said leading edge is most proximate said said foils having similar shapes including a leading magnetizable armatures to the time when said trailedge and a trailing edge, ing edge is most proximate said magnetizable armasaid leading edges being aligned with each other and tures, said trailing edge of said second foil lying intermedisaid magnetic means comprising a rotatable disk of ate said edges of said first foil, and

very low permeability material and two radial foils means transporting said interposer and moving said of high permeability affixed thereto both having leadfoils into and out from the interposed position to ing and trailing edges, effect the opening and closing of said switch. said leading edge of said one magnetic area comprises 6. A switching unit according to claim 5 wherein:

the leading edges of both said foils, said interposer is a cyclically rotatable disk,

said magnet, a-rmatures and foil edges are oriented radial of the axis of rotation of said disk, and

said foils in combination shunt sufficient flux to open the switch at the time the cyclically rotatable disk positions the aligned leading edges of the foils radially coincident with said armatures and to close the switch when the trailing edge of said first foil is radially coincident with said armatures.

7. A switching unit according to claim 6 further comprising:

a pair of non-magnetic members fixedly supporting in parallel, spaced apart relation said magnet and switch,

a flux shunting shield fixed proximate to said switch on one of said support members, and

a flux shunting shield fixed proximate to said magnet on the other of said support members,

said shields positioned parallel to the faces of said interposed disk and lying more distant therefrom than said magnet and said switch.

References Cited by the Examiner UNITED STATES PATENTS Stanaway 20087 Vanden Broeck 20087 Hall 20087 Jackson et a1. "20087 

1. IN COMBINATION WITH A MAGNETICALLY OPERABLE SWITCH AND AN ADJACENTLY FIXED MAGNET, SAID SWITCH HAVING ARMATURE MEANS HELD IN ONE POSITION BY MAGNETIC ENERGY FROM SAID MAGNET AND OPERABLE TO ANOTHER POSITION BY SHUNTING MAGNETIC ENERGY FROM SAID SWITCH ARMATURE MEANS, MAGNETIC ENERGY SHUNTING MEANS COMPRISING: A CYCLICALLY DRIVEN NON-MAGNETIC DISK INTERPOSED BETWEEN SAID SWITCH AND SAID MAGNET, AND A PLURALITY OF DISCRETE ARCUATE SEGMENT MAGNETIC ELEMEANS CARRIED BY SAID DISK ON AT LEAST ONE OF ITS SURFACES, SAID MAGNETIC ELEMENTS PROXIMATELY POSITIONED WITH RESPECT TO ONE ANOTHER AND IN COMBINATION EFFECTING A FIRST QUANTUM OF MAGNETIC ENERGY SHUNTING WHEN CARRIED BY SAID DISK INTO INTERPOSING POSITION BETWEEN SAID SWITCH AND SAID MAGNET, 